Gut flora dictates how much weight we can lose

A new Danish study has revealed that the proportion of some bacteria in the gut may be responsible for how much weight we are able to lose, and under what circumstances. General dietary guidelines targeting whole populations may therefore be less effective than previously believed.

Is your weight loss plan not working? It may all be down to your gut bacteria, researchers say.

Lately, studies investigating the role of gut bacteria in our overall health – especially in the context of metabolic disorders such as obesity – abound. For instance, earlier this week, Medical News Today reported on a study looking into how some gut bacteria may influence weight gain.

Now, new research from the Department of Nutrition, Exercise and Sports at the University of Copenhagen in Denmark examines how our individual gut microbiomes may shed light on whether or not – and to what extent – we are able to lose excess weight while following particular dietary guidelines.

As study co-author Prof. Arne Astrup explains, “Human intestinal bacteria have been linked to the increasing prevalence of overweight and obesity, and scientists have started to investigate whether the intestinal bacteria can play a role in the treatment of overweight.”

“But it is only now that we have a breakthrough demonstrating that certain bacterial species play a decisive role in weight regulation and weight loss,” he says.

The study’s findings were recently published in the International Journal of Obesity.

Gut bacteria ratio key to weight regulation

The study recruited 54 participants. Of these, 31 were set to follow the New Nordic Diet, which is a set of Danish national dietary guidelines promoting “fruit, vegetables, fiber, and whole grains.” The purpose of this diet is to help shed excess weight and maintain a healthful body mass index (BMI).

The other 23 participants followed the Average Danish Diet, which typically includes more meat and processed foods.

All the participants followed their respective diets for a total of 26 weeks. At the end of this period, the 31 people on the New Nordic Diet had lost an average of 3.5 kilograms, while the other 23 had shed an average of 1.7 kilograms.

However, although the New Nordic Diet was found to be more efficient in promoting weight loss than a regular diet overall, the researchers also noted that the participants’ individual gut bacterial profiles had an important role to play.

Prof. Astrup and colleagues saw that participants who had a higher ratio of Prevotella-to-Bacteroides bacteria shed more weight when following a New Nordic Diet compared with people who followed an Average Danish Diet.

At the same time, people with a low ratio of Prevotella-to-Bacteroidesbacteria did not shed any more weight when following the New Nordic Diet. The researchers also noted that around half of the population has a higher Prevotella-to-Bacteroides proportion.

In conclusion, the team explains, only 50 percent of the population is likely to shed excess weight if they follow the new Danish dietary recommendations, while the other half will remain unaffected.

“The study shows that only about half of the population will lose weight if they eat in accordance with the Danish national dietary recommendations and eat more fruit, vegetables, fibers, and whole grains. The other half of the population doesn’t seem to gain any benefit in weight from this change of diet,” says first study author Prof. Mads Fiil Hjorth.

One size does not fit all

Prof. Hjorth suggests that individuals less likely to lose weight or stay in shape following such dietary guidelines “should focus on other diet and physical activity recommendations until a strategy that works especially well for them is identified.”

They suggest that it may be more helpful to come up with “bespoke” dietary guidelines, tailored to individual needs, rather than trying to find “recipes for success” for whole populations.

Biomarkers such as stool or blood samples could help healthcare professionals to devise more appropriate diets, the researchers explain.

“This is a major step forward in personalized nutritional guidance. Guidance based on this knowledge of intestinal bacteria will most likely be more effective than the ‘one size fits all’ approach that often characterizes dietary recommendations and dietary guidance.”

Prof. Mads Fiil Hjorth

The researchers also point out that their findings are solid; they have been confirmed through two independent studies.